1. Field of the Invention
The present invention relates to a device for correcting a taught point in an operation program of a robot. The present invention also relates to a program and a recording medium, for correcting a taught point in an operation program of a robot. The present invention further relates to a method for correcting a taught point in an operation program of a robot.
2. Description of the Related Art
An industrial robot (hereinafter referred to simply as a robot) operates so as to follow a certain operation program (or a task program). When a plurality of operation programs are prepared, which correspond to the types of tools (or end effecters) attached to the robot, the types of objective workpieces, the contents of operations, etc., and are given to a robot, the robot can execute various kinds of tasks. For example, in a spot welding robot, when a vehicle body to be welded is newly and additionally provided, a new welding-operation program including data of weld points on the vehicle body is prepared. In this case, if an existing welding gun attached to the robot tends to interfere with surrounding objects (such as a jig or a vehicle body part) during the welding of the newly provided vehicle body, the existing gun is replaced with another welding gun having such a shape as to avoid interference, and a new welding-operation program suitable for the other welding gun is prepared.
In order to prepare an operation program to control the operation of a robot, an operator makes the respective control axes of the robot run in a manual mode at low speed, generally by using an operating panel or “a teach pendant”, so as to sequentially position a tool at a plurality of working points at which a task is performed on a workpiece, and thereby makes the robot store the working points as “taught points”. The robot stores the actual positions of the respective control axes at an instant the tool is positioned at each of the working points, as the information of position and orientation of the robot at each of the taught points (referred to as “position data of a taught point” in the present application). In this connection, it is also known to perform the above programming by teaching, through an offline simulation using a personal computer or the like.
When a new operation program is required to be prepared, e.g., the addition of a new workpiece, it is possible to meet such requirement by correcting the position data of desired taught point(s) among the previously stored taught points, except for a new working point that should be newly stored in the robot as an additional taught point. Conventionally, in order to correct the taught point(s), a measure has been performed wherein the position data of taught points, relating to all of the working points required to be modified, are corrected one by one. For example, Japanese Unexamined Patent Publication (Kokai) No. 2004-280529 (JP-A-2004-280529) discloses a taught-point correcting device for correcting, one by one, the position data of a plurality of taught points included in an operation program of a robot.
In a case where an item to be produced is added in a highly automated manufacturing system using a robot, a production line is required to be modified. In this connection, a large number of actions are required to redesign various kinds of hardware, such as a jig, a machine, a conveyor, etc., and to prepare various kinds of software, such as a processing program of a processing machine, an operation program of a robot, a sequence ladder and a production management program of a programmable controller (PC) or a production management device, etc. Effectively reducing the number of actions required to construct the hardware/software, so as to deal with a modification of the production line, has been recognized as a significant problem relating to costs in the automated manufacturing system, and therefore it is desirable to decrease the number of steps for preparing an operation program of a robot.
In some cases, after starting the operation of a manufacturing system, it is required to adjust a taught point included in the operation program of a robot. Such adjustment may involve correction of a bolt position at which a bolt is fastened by a nut runner, fine adjustment of a holding position at which a workpiece is held by a hand, and so on. The adjustment of the taught point depends on the processing or dimensional accuracy of a workpiece, and therefore the necessity of adjustment generally cannot be clearly recognized before the manufacturing system starts to operate. In this connection, there is a case where the position data of several taught points included in an operation program have a certain correlation with each other, or the same taught point is included in several different operation programs. In such a case, it is essential for the operator to be skilled in a teach-programming, and further to systematically understand in detail the contents of all of operation programs given to the robot, so as to properly adjust the taught points. Also, in the above-described conventional measure correcting one by one the position data of taught points relating to all of the working points required to be modified, the workload of an operator may increase considerably, which may result in erroneous or undesirable corrections. Further, the stored information before correction is usually lost by correcting the data of taught points, and therefore in a case where an erroneous or undesirable correction has been performed, it is difficult to restore the position data of taught points to a state before correction.